In vitro induction of segregational errors of chromosomes in cultured human lymphocytes by cannabinoids and olivetol is being investigated. The errors observed include chromosome bridge formation, anaphase lag, unequal segregation of chromosomes and multipolar division. The effects of these drugs are being studied in both short and long-term cultures, the latter with an aim to establish clones of cells with hypoploid complements. Possible mutagenetic effects of marihuana smoking is being studied in fertilized mice ova. Early gestational products from female mice exposed to marihuana smoke are examined for their ability to synthesize macromolecules. The basis of increased mitotic index found in cultured lymphocytes of heroin addicts is being studied in vitro. Macromolecular synthesis of lymphocytes exposed to morphine sulfate is being examined.